var XMLParser = require("fast-xml-parser").XMLParser;
var http = require("http");
var https = require("https");
var fs = require("fs");
var MongoClient = require('mongodb').MongoClient;
var nodemailer = require("nodemailer");

var transporter = nodemailer.createTransport({
  host: "localhost",
  port: 25,
  secure: false, // Use `true` for port 465, `false` for all other ports
  tls: {
    rejectUnauthorized: false
  },
  pool: true
});

var fromEmail = "root@localhost";
var mongoURL = "mongodb://localhost/newsletter";
var dbname = "newsletter";

function antiXSS(string) {
  return string.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;").replace(/"/g, "&quot;").replace(/'/g, "&apos;");
}

function escapeRegExp(string) {
  return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
}

function connectMongo(callback) {
  MongoClient.connect(mongoURL, function (err, db) {
    if (err) throw err;
    var dbo = db.db(dbname);
    dbo.createCollection("emails", function (err, dbres) {
      dbo.createCollection("posts", function (err, dbres) {
        callback(dbo);
      });
    });
  });
}

function formatTemplate(templateName, templateData, callback) {
  fs.readFile(__dirname + "/" + templateName + ".template", function (err, data) {
    if (err) throw err;
    var tD = data.toString();
    Object.keys(templateData).forEach(function (key) {
      tD = tD.replace(new RegExp("\\{\\{" + escapeRegExp(key) + "\\}\\}", "g"), templateData[key]);
    });
    callback(tD);
  });
}

https.get("https://blog.svrjs.org/atom.xml", function (res) {
  var data = "";
  res.on("data", function (chunk) {
    data += chunk.toString();
  });
  res.on("end", function () {
    var parser = new XMLParser();
    var parsedData = parser.parse(data);
    var entries = parsedData.feed.entry;
    connectMongo(function (db) {
      db.collection("emails").find({}).toArray(function (err, emails) {
        if (err) throw err;
        var queue = [];
        var ent = JSON.parse(JSON.stringify(entries)).reverse();

        function getEntriesId(_id) {
          if (!_id) _id = 0;
          if (_id >= ent.length) {
            process.exit(0);
            return;
          }
          db.collection("posts").find({
            id: ent[_id].id
          }).toArray(function (err, result) {
            if (err) throw err;
            if (result.length == 0) {
              db.collection("posts").insertOne({
                id: ent[_id].id
              }, function (err, dbres) {
                if (err) throw err;
                var _qid = _id;

                function sendEmail(_id) {
                  if (!_id) _id = 0;
                  if (_id >= emails.length) {
                    getEntriesId(_id + 1);
                    return;
                  }
                  var qim = ent[_qid].id.match(/https:\/\/blog\.svrjs\.org\/[0-9]+\/[0-9]+\/[0-9]+\/([^\/]+)/);
                  var imageURL = "https://blog.svrjs.org/images/covers/" + (qim ? qim[1] : "missing") + ".png";
                  formatTemplate("index.html", {
                    "title": antiXSS(ent[_qid].title),
                    "summary": ent[_qid].summary.replace(/ (src|href)="\/(?!\/)/g," $1=\"https://blog.svrjs.org/"),
                    "image": antiXSS(imageURL),
                    "link": antiXSS(ent[_qid].id),
                    "unsubscribe": antiXSS("https://newsletter.svrjs.org/unsubscribe.svr?id=" + encodeURIComponent(emails[_id].unsubscribeId))
                  }, function (data) {
                    transporter.sendMail({
                      from: fromEmail,
                      to: emails[_id].email,
                      subject: ent[_qid].title + " - SVR.JS Blog Newsletter",
                      text: 'This message requires HTML to be viewed',
                      html: data
                    }, function (err, info) {
                      if (err) throw err;
                      sendEmail(_id + 1);
                    });
                  });
                }
                sendEmail();
              });
            } else {
              getEntriesId(_id + 1);
            }
          });
        }
        getEntriesId();
      });
    });
  });
});